Tank-style water heaters generally comprise a water storage container or tank with water inlet and outlet connections and with a thermostatically controlled heating source to heat a body of contained water to, and maintain the water at, a predetermined temperature. Electricity or natural or propane gas are the most common heat sources used for both residential and commercial water heaters.
In electric water heaters, the heating element is commonly submerged within the water tank to apply heat directly to the water. By contrast, gas-fueled water heaters have a separate combustion chamber disposed immediately beneath the water tank, in which a gas burner is situated to apply heat to the tank for heating the water contained therein. In turn, provision must be made for exhausting the by-products of the fuel combustion process. For this purpose, substantially all fuel-burning water heaters are equipped with an exhaust flue extending upwardly from the combustion chamber through the water tank and outwardly therefrom for exhausting the combustion by-products. This configuration provides the additional benefit of providing supplementary heating to the contained water as the hot combustion by-products travel upwardly through the flue.
Because the natural chimney effect of rising combustion by-products within an exhaust flue provides relatively inefficient heat exchange to the surrounding water within a water heater storage tank, it has become commonplace to provide a baffle arrangement within the exhaust flues of fuel-burning water heaters to interrupt natural laminar flow of the by-products and thereby increase residence time of combustion by-products within the exhaust flue to obtain increased heat transfer to the surrounding water. While such baffle arrangements are generally effective to accomplish greater heat exchange than in water heaters without such baffle arrangements, known baffle arrangements have disadvantages. Many known baffle arrangements require welding of individual component parts which undesirably add to the overall cost of water heaters. Other baffle arrangements impose an undesirably higher pressure drop across the height of the exhaust flue. Especially in water heaters that rely upon a natural upward thermal draft for exhaustion of combustion by-products, the hydrostatic pressure naturally occurring along the height of the exhaust flue may be quite small, and accordingly, a baffle arrangement imposing a greater pressure drop can impede proper exhaust of combustion by-products and risk a dangerous build up of carbon dioxide in the ambient environment surrounding the water heater.